HD 217107 c

Planetbox begin
name = HD 217107 cPlanetbox star
star = HD 217107
constell = Pisces
ra = RA|22|58|15.54
dec = DEC|−2|23|43.39
dist_ly = 64.3 ± 1
dist_pc = 19.7 ± 0.3
class = G8IVPlanetbox orbit
separation =
position_angle =
semimajor = 4.41 ± 0.21
semimajor_no_units =
eccentricity = 0.537 ± 0.026
period = 3352 ± 157
period_year = 9.18 ± 0.43
inclination =
ang_dist = 119.189
long_peri = 164
arg_peri =
t_peri = 2,450,921 ± 84
t_peri_no_jd =
t_transit =
t_transit_no_jd =
t_approach =
semi-amp = 34 ± 20Planetbox character
mass = >2.5 ± 0.48
radius = ~1.029
density =
gravity =
temperature = ~132Planetbox discovery
discovery_date = 24 November 1998
24 June 2005 (confirmed)
discoverers = Marcy "et al."
discovery_method = Doppler spectroscopy
discovery_site = flag|United States
discovery_status = Confirmed

HD 217107 c is an extrasolar planetcite journal | url=http://www.journals.uchicago.edu/doi/full/10.1086/432901 | author=Vogt "et al." | title=Five New Multicomponent Planetary Systems| journal=The Astrophysical Journal| year=2005 | volume=632 | issue=1 | pages=638–658 | doi=10.1086/432901] approximately 46 light-years away in the constellation of Pisces (the Fish). The planet was the second planet to be discovered orbiting the star HD 217107. HD 217107 c's existence was hypothesised in 2002 and confirmed in 2005, when radial velocity studies of the star indicated another, more distant and massive companion orbiting the star. The planet is though to be a Jupiter twin planet, but its mass and orbital parameters remain highly uncertain.

Detection and discovery

A study of the radial velocity of HD 217107 carried out in 1998 revealed that its motion along the line of sight varied over a 7.1 day cycle, indicating the presence of a planet in orbit around the star. The planet was designated HD 217107 b, and was found to be somewhat heavier than Jupiter, and orbiting extremely close to the parent star in an orbit with quite a large eccentricity. cite journal | url=http://www.journals.uchicago.edu/doi/full/10.1086/316304 | author=Fischer "et al." | title=Planetary Companions around Two Solar-Type Stars: HD 195019 and HD 217107 | journal=Publications of the Astronomical Society of the Pacific | year=1999 | volume=111 | issue=755 | pages=50–56 | doi=10.1086/316304]

Most planets with orbital periods of less than 10 days have almost circular orbits, and its discoverers proposed that the high eccentricity of HD 217107 b's orbit could be due to the gravitational influence of a second planet in the system at a distance of several astronomical units (AU). [ cite journal | url=http://www.journals.uchicago.edu/doi/full/10.1086/320224 | author=Fischer "et al." | title=Planetary Companions to HD 12661, HD 92788, and HD 38529 and Variations in Keplerian Residuals of Extrasolar Planets | journal=The Astrophysical Journal | year=2002 | volume=551 | issue=2 | pages=1107–1118 | doi=10.1086/320224 ] Confirmation of the existence of the second planet followed in 2005, and it was designated HD 217107 c.

Observations of the star's radial velocity variations indicate a period of about 8 years, and HD 217107 c's mass is thought to be at least twice that of Jupiter in a very eccentric orbit with a semimajor axis of about 4 AU. Large uncertainties still exist in these measurements, though, due to the length of the orbital period and the distance of HD 217107 c from its parent star.

See also

* 47 Ursae Majoris b
* HD 217107 b

References

External links

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